United faced a public outcry after videos circulated online showing a passenger being forcibly dragged off a flight for refusing to give up a seat he paid for. United did not apologize quickly enough, and when the apology came, it was half-hearted.

As it began to recall millions of cars over gas pedal problems, the U.S. National Highway Traffic Safety Administration accused the automaker of trying to skirt responsibility by sending Toyota owners "inaccurate and misleading information."

Toyota took a long time to identify the issue and take responsibility for the problem -- gas pedals were sticking and causing crashes.

This slow, bungled response did severe damage to the Toyota brand and hurt sales in Japan, North America and Europe.

If your firm gets into a PR crisis, it's critical to acknowledge the problem and issue a swift apology.

3. Make the necessary changes

Once the diagnosis is clear, organizations need to act -- and be seen to act -- to make the changes that will prevent similar problems in the future.

Only a full-scale intervention will be seen to be credible and authentic.

Organizations need to understand that rebuilding trust with the public takes time.

They should continue to evaluate their actions to ensure they are fully addressing the causes of the crisis. They also need to be transparent in their work and investigations.

In this respect, BP(BP) has got it right -- they have consistently updated and reported on the actions that they have taken since the Gulf of Mexico oil spill, which has helped the company rebuild its image.